Optimization of spine surgery outcomes in patients with osteoporosis: a comprehensive narrative review
Article information
Abstract
Osteoporosis has emerged as a major challenge in spine surgery amid the rapid aging of the global population. Diminished bone quality significantly heightens the risk of postoperative mechanical complications following spinal instrumentation, including screw loosening, proximal junctional kyphosis and failure, cage subsidence, pseudoarthrosis, and loss of surgical correction. These complications often result in poorer clinical outcomes, higher healthcare expenditures, and an increased need for revision surgery. Comprehensive preoperative assessment of bone health represents the initial step in optimizing surgical outcomes in patients with osteoporosis. While dual-energy X-ray absorptiometry remains the gold standard for evaluating bone mineral density, opportunistic computed tomography-based assessments can further refine risk stratification. Secondary causes of osteoporosis should be identified and managed preoperatively. Surgical strategies should prioritize maximizing pedicle screw fixation and minimizing implant-related complications. Key technical considerations include optimization of screw trajectory, diameter, and length; judicious use of cement augmentation; appropriate sacral fixation techniques; and meticulous preservation of vertebral endplates to prevent cage subsidence. In selected cases, the cortical bone trajectory may offer biomechanical advantages for osteoporotic bones, while perioperative pharmacologic optimization further enhances outcomes. Anabolic agents, such as teriparatide, augment bone formation and fusion rates and are recommended as first-line therapy when feasible. Antiresorptive agents typically serve as second-line or maintenance therapy following anabolic treatment. A comprehensive approach integrating systematic bone health assessments, optimized surgical techniques, and appropriate pharmacological management is essential to mitigate implant-related complications and improve surgical outcomes in patients with osteoporosis.
Introduction
Osteoporosis, characterized by reduced bone mass and deterioration of bone structure, has become an increasingly significant issue in spine surgery due to the rapid aging of the global population [1]. Older adults with degenerative spinal diseases frequently require spinal fusion procedures; however, osteoporosis substantially increases the risk of postoperative mechanical complications. Screw loosening, proximal junctional kyphosis (PJK), proximal junctional failure (PJF), cage subsidence, loss of correction, and pseudoarthrosis are observed more frequently in patients with osteoporosis, often leading to poor clinical outcomes and increased rates of revision surgery [2–5]. Furthermore, patients with osteoporosis experience higher healthcare costs, greater transfusion requirements, and prolonged anesthesia times compared with those without osteoporosis [3].
Pedicle screw (PS) fixation remains the cornerstone of spinal stabilization; however, its pullout strength is closely related to bone mineral density (BMD) and vertebral microarchitecture. In osteoporotic vertebrae, diminished trabecular bone quality and increased fragility substantially reduce PS pullout strength and insertional torque [6,7]. Previous studies have reported screw loosening rates exceeding 30% in osteoporotic populations, particularly at the sacrum, ranging from 15.6% to 46.5%, due to its distinct anatomical structure and biomechanical properties [8,9]. With the growing number of older adults undergoing spinal fusion, spine surgeons are increasingly encountering implant failure associated with osteoporosis [3,10].
Recent developments in imaging-based bone quality assessment, PS fixation techniques, and osteoporosis-directed pharmacologic treatments offer new opportunities to mitigate complication rates and achieve outcomes comparable to those in nonosteoporotic populations [5,11,12]. Despite growing evidence, clinical decision-making concerning fixation strategies and perioperative bone optimization remains variable, and standardized consensus guidelines are still lacking. Therefore, this narrative review summarizes the current evidence regarding the impact of osteoporosis on spine surgery outcomes and highlights contemporary surgical and medical strategies to optimize surgical outcomes in this high-risk population.
Optimization of Spine Surgery Outcomes in Patients with Osteoporosis
Strategies to optimize outcomes in osteoporotic spine surgery are enumerated in Table 1.
Strategies for optimizing outcomes in osteoporotic spine surgery
Assessment of osteoporosis
Since osteoporosis substantially predisposes patients to mechanical complications after spinal instrumentation, accurate preoperative diagnosis allows implementation of strategies to optimize surgical outcomes and minimize postoperative complications [11,12]. However, a survey of spine surgeons revealed only 60% assessed BMD following a fragility fracture, 40% performed preoperative BMD evaluation before spinal fusion, and only 18% investigated underlying metabolic abnormalities [13]. Therefore, systematic osteoporosis assessment should be regarded as the first step in preparing patients with osteoporotic spine conditions undergoing spinal instrumentation [11,14,15].
Bone health assessment should be performed in all patients before elective spinal reconstructive surgery, including the evaluation of BMD and serum 25-hydroxyvitamin D levels. Dual-energy X-ray absorptiometry (DXA) is the gold standard method for BMD evaluation and osteoporosis diagnosis and is recommended prior to spinal instrumentation in all patients aged ≥65 years, regardless of sex or additional risk factors. In patients younger than 65 years, DXA screening is recommended when risk factors for impaired bone health are present, including chronic corticosteroid use, prior hip or spine fragility fractures, metabolic bone disease, cancer treatments affecting bone metabolism, or chronic kidney disease (Fig. 1) [11,14–16]. According to World Health Organization diagnostic criteria, patients are classified as having osteoporosis with a T-score of ≤−2.5, osteopenia with a T-score between −2.5 and −1, and normal BMD with a T-score ≥−1 [17]. In patients aged 20–50 years, Z-scores should be employed to evaluate of BMD [11].
Indications for bone mineral density evaluation prior to elective spine reconstructive surgery. FRAX, Fracture Risk Assessment.
Although hip and spinal DXA is the gold standard for evaluating BMD, degenerative spinal changes may occasionally lead to an overestimation of lumbar BMD. Additionally, the presence of fractures and prior spinal or hip surgery with implanted hardware can compromise the accuracy and interpretability of BMD measurements. In these situations, one-third radius BMD measurements provide a more reliable assessment [11,16]. In addition, opportunistic preoperative computed tomography (CT) is useful for identifying at-risk patients. This technique involves placing a measurement area over the trabecular bone of the L1 vertebra while excluding the cortical bone and osteophytes [11,18,19]. Although a CT-based Hounsfield unit (HU) value ≤100 is generally considered suggestive of osteoporosis, patients with HU values ≤150 have also been recommended to undergo formal DXA evaluation to confirm the diagnosis and guide perioperative management [11,18]. In patients with poor bone health, evaluation for potential secondary causes of osteoporosis should be performed, and reversible conditions should be treated before surgery [11,15]. Patients with confirmed osteoporosis should be counseled regarding the elevated risk of postoperative complications. Furthermore, appropriate surgical and pharmacologic strategies should be applied to optimize outcomes following spinal instrumentation [11,14].
Surgical strategies to optimize surgical outcomes
Because compromised bone strength directly increases the risk of implant-related complications following spinal instrumentation, surgical strategies for patients with osteoporosis should aim to enhance screw fixation and minimize implant failure after surgery. Several technical approaches have been proposed to improve surgical outcomes in patients with osteoporosis, including optimization of PS trajectory and dimensions, selective cement augmentation, and preservation of vertebral endplates for interbody fusion [4–6,12].
Optimization of PS fixation
Optimization of PS fixation to improve the bone-screw interface is a key strategy for mitigating implant-related complications in osteoporotic spine surgery. Previous studies have shown that the screw pullout strength is affected not only by BMD but also by screw trajectory, diameter, and length [12,20,21]. The optimal PS trajectory involves positioning the screw within the upper third of the vertebral body in the sagittal plane, aligned parallel to or directed toward the superior endplate, while achieving the highest feasible degree of convergence permitted by the anatomy to enhance pullout strength and resistance to screw loosening [21–23]. PS diameter directly influences its proximity to the cortical bone and the screw-pedicle fill ratio, both of which are critical determinants of pullout strength and resistance to flexion-extension loading [24]. Increasing the screw diameter can substantially improve the mechanical stability of the screw-bone interface, particularly in osteoporotic spines [25]. PS is characterized by distinct inner and outer diameters. A larger outer diameter combined with a smaller core diameter may enhance fixation strength and decrease the risk of screw loosening [26]. Previous studies have also demonstrated that PS length influences resistance to lateral bending and axial rotational loads, as well as the distribution of mechanical stress at the bone-screw interface [24]. The ratio of screw length to vertebral body height is a critical determinant of fixation strength and intravertebral stress distribution, consistent with the principles of lever mechanics [27]. Greater screw depth augments anchorage within the vertebral body, whereas incomplete thread purchase may result in localized stress concentration, thereby increasing the risk of screw breakage and loosening [28]. Consequently, when anatomical conditions permit, selecting the longest and widest PS that can be safely accommodated within the pedicle is recommended to improve the fixation of osteoporotic vertebrae (Fig. 2).
A 73-year-old female patient diagnosed with degenerative spinal stenosis, diabetes mellitus, chronic kidney disease and osteopenia (T –1.6). Postoperative anteroposterior (A) and lateral (B) spine radiographs following oblique lumbar interbody fusion are shown. The longest and largest possible pedicle screws within safe pedicle boundaries were inserted into the upper one-third of the vertebral body in the sagittal plane, aligned parallel to the superior endplate, while achieving the maximal feasible convergence. Cage subsidence is observed at the L2–3 level. Preservation of the bony endplates during intervertebral disc preparation is critical in preventing cage subsidence, particularly in patients with osteoporosis.
Instrumentation at the lumbosacral junction is particularly challenging because this region is highly susceptible to screw loosening due to high mechanical stress, wide diameter, short sacral pedicle length, and relatively poor sacral bone quality [29,30]. Therefore, bicortical or tricortical S1 PS fixation techniques have been employed to enhance screw purchase by allowing screw tips to engage additional sacral cortical bone. Previous studies have demonstrated that these approaches provide greater fixation strength than conventional unicortical fixation; however, screw loosening may still occur in osteoporotic patients, especially following long-segment fusion [8,31]. However, bicortical and tricortical PS fixation may increase the risk of injury to the major neurovascular structures anterior to the sacrum because of their close anatomical proximity [32]. Accordingly, careful selection of appropriate sacral fixation techniques is essential when performing lumbosacral fusion in osteoporosis patients.
In osteoporotic bone, undertapping may both enhance insertional torque and pullout strength. In a biomechanical analysis of thoracic PS fixation, Kuklo and Lehman [33] demonstrated that 1 mm undertapping, compared to 0.5 mm undertapping, was linked to a 47% increase in maximal insertion torque, thereby supporting undertapping as a strategy to boost fixation strength. However, its effectiveness depends on meticulous hole preparation, including matching the thread pitch between the tap and PS, as mismatches can impair fixation strength [34,35].
Cortical bone trajectory
Cortical bone trajectory (CBT) is an alternative fixation approach with specific advantages in osteoporosis patients. By following a medial-to-lateral path in the transverse plane and a caudal-to-cephalad path in the sagittal plane, CBT maximizes cortical bone engagement while reducing reliance on compromised trabecular bone [27,36,37]. Finite element analyses and biomechanical studies have shown that CBT provides increased pullout strength and lowers stress on interbody cages and screws compared to traditional trajectories in healthy and osteoporotic bone [27,36–38]. In a clinical study of patients with osteoporosis, Liu et al. [39] demonstrated that CBT achieved superior outcomes compared to conventional trajectories, with significantly decreased screw loosening rates (6.5% vs. 28.13%) and reduced cage subsidence.
In addition, a meta-analysis revealed that CBT is a less invasive technique that minimizes soft tissue dissection, resulting in reduced postoperative complications, shorter surgical duration, and lower blood loss while achieving fusion rates comparable to those of traditional trajectories [40]. However, CBT has a technical learning curve, and the relatively shorter screw length and limited anterior column purchase may compromise construct rigidity in long-segment fusion or deformity correction procedures [41]. Biomechanical studies have suggested that the optimal screw dimensions for CBT are a diameter ≥5.5 mm and a length ≥35 mm [27].
Cement augmentation of pedicle screws
Cement augmentation of PS has been widely utilized to effectively improve screw fixation in patients with osteoporosis, particularly when conventional PS fixation is inadequate due to severely reduced bone strength. Augmentation with polymethylmethacrylate augments the bone-screw interface strength, mitigates the risk of screw loosening, improves fusion rates, preserves intervertebral height, and is linked to superior long-term clinical outcomes compared to conventional PS fixation in the osteoporotic spines [5,6]. Recently, fenestrated PSs with one or two distal fenestrations have been increasingly adopted to facilitate cement augmentation (Fig. 3) [5,8].
A 69-year-old female patient diagnosed with degenerative spinal stenosis and osteoporosis (T –2.6). One-year follow-up anteroposterior (A) and lateral (B) spine radiographs are presented, along with sagittal (C), coronal (D), and axial (E) computed tomography images following posterior lumbar interbody fusion and posterolateral fusion. Cement was properly injected around the fenestrated pedicle screws without a clear zone, screw pullout, or screw migration. Arrows indicate the two holes of the fenestrated pedicle screw.
High-risk criteria warranting consideration for cement augmentation include age >65 years, osteoporosis, chronic kidney disease, and autoimmune diseases. The presence of two or more risk factors is a strong indication for cement augmentation [42]. Son et al. [5] reported that cement-augmented screws reduce radiological implant-related complications, including screw loosening and loss of correction, compared with conventional PS fixation in patients with osteoporosis, despite the cement-augmented group being comprised of participants who were significantly older and had lower T-scores. Comparative studies by Gu et al. [8] revealed that sacral fixation with cement augmentation provided superior outcomes in osteoporotic spines compared to bicortical or tricortical fixation alone. These findings suggest that cement augmentation effectively minimizes screw loosening while avoiding the increased risk of major neurovascular injury associated with anterior cortical penetration. Furthermore, cement augmentation of the PS at the upper instrumented vertebra has been shown to significantly lower PJF incidence in adult spinal deformity surgery among patients with low BMD or osteoporosis, primarily through enhancement of PS pullout strength [43].
However, cement augmentation is associated with several potential complications, including cement leakage, pulmonary embolism, neurovascular complications, and increased technical difficulty during revision surgery. Among these, cement leakage is the most commonly reported, with incidence rates ranging from 38.3% to 93.6%. Although frequently observed on imaging, it is usually clinically asymptomatic. Technical modifications, such as restricting cement volume (approximately 1.5–2.5 mL per lumbar screw and 1 mL per thoracic screw), injecting during the dough phase, using slow controlled injection, and maintaining continuous fluoroscopic monitoring, have been shown to substantially reduce the incidence of cement leakage. In addition, cement delivery through fenestrated screws via a specialized tube, rather than pre-injecting cement prior to conventional screw insertion, may reduce the risk of cement leakage [5,6,8,44,45].
Prevention of cage subsidence
Cage subsidence is a frequent implant-related complication following interbody fusion procedures, particularly in patients with osteoporosis, in whom reduced vertebral bone strength predisposes to endplate collapse. Several studies have shown that a lower BMD is linked to an increased risk of cage subsidence after lumbar interbody fusion. However, cage subsidence does not always result in clinical deterioration [4,46–48].
In addition to osteoporosis, excessive disc height restoration during surgery is an independent risk factor for cage subsidence. Overdistraction of the disc space increases loading on compromised endplates, promoting cage subsidence and potential loss of restored disc height. These findings highlight the importance of achieving disc height restoration in a controlled manner while avoiding excessive distraction [48,49].
Preservation of bony endplates during intervertebral disc preparation is crucial in preventing cage subsidence. Excessive endplate removal may damage the bony endplate and weaken structural support for interbody cages, thereby predisposing to subsidence. Accordingly, in patients with osteoporosis, meticulous endplate handling aimed at preserving the bony endplate and facilitating even load distribution across the endplate surface can help minimize subsidence risk [4,48,49].
Pharmacologic strategies to optimize surgical outcomes
Anabolic agents
In addition to surgical optimization, perioperative pharmacological treatment of osteoporosis may further reduce implant-related complications and enhance fusion outcomes. Anabolic agents have demonstrated beneficial effects in patients with osteoporosis undergoing spinal fusion [2]. Teriparatide, a recombinant form of the human parathyroid hormone, stimulates osteoblastic activity and promotes new bone formation when administered intermittently, leading to increased bone mass and improved bone microarchitecture. By promoting bone formation at the bone-implant interface and accelerating fusion, perioperative teriparatide treatment has been shown to be associated with reduced screw loosening, prevention of cage subsidence, and higher fusion rates following spinal instrumentation, supported by high-grade evidence (grade B) [7,47,50]. More recently, romosozumab, an antisclerostin antibody with dual anabolic and antiresorptive effects, has been shown to rapidly increase vertebral body BMD and BMD around the PS [51]. Sawada et al. [52] reported that perioperative administration of romosozumab effectively increased BMD and reduced PJK risk, particularly fracture-related PJK, as well as other osteoporosis-related complications in patients undergoing adult spinal deformity surgery. Emerging evidence suggests that romosozumab treatment may provide early reinforcement of vertebral structural integrity, making it a potential anabolic option for bone optimization in patients with osteoporosis requiring spinal surgery. Although the optimal duration of perioperative anabolic agent therapy remains uncertain, an expert consensus by Sardar et al. [11] recommends initiating anabolic agents at least 2 months and up to 6 months before elective multilevel spinal reconstructive surgery, with continuation for a minimum of 8 months postoperatively to optimize surgical outcomes.
Antiresorptive agents
Antiresorptive agents, including bisphosphonates and denosumab, are widely employed for managing osteoporosis and are recommended as second-line options before spinal instrumentation when anabolic therapy is contraindicated or unavailable [11]. Although concerns have been raised regarding potential delays in fusion due to inhibition of bone turnover, available clinical evidence indicates that bisphosphonates do not significantly impair fusion rates [53]. While perioperative bisphosphonate use has been linked to lower incidence of screw loosening and adjacent-level vertebral fracture, the supporting evidence is limited, corresponding to grade C recommendations [14,53]. Denosumab, a human monoclonal antibody targeting RANKL, is supported by high-level evidence exhibiting enhanced fusion rates and increased screw pullout strength, making it an effective treatment option for patients with osteoporosis. Accordingly, denosumab may be recommended as a grade B alternative when anabolic therapy is contraindicated or not feasible due to cost [53,54]. Following the completion of anabolic therapy, transition to antiresorptive therapy is recommended to preserve therapeutic benefits and sustain gains in BMD [11].
Adjunctive therapies
Adequate calcium and vitamin D3 supplementation prior to spinal instrumentation is recommended to optimize surgical outcomes. Unless contraindicated, all patients should be administered a total daily calcium intake of 1,000–1,200 mg through diet and/or supplementation. In addition, vitamin D3 supplementation of 1,000–2,000 IU per day is recommended for patients with osteoporosis or documented vitamin D insufficiency or deficiency [11].
Conclusions
Successful spine surgery in patients with osteoporosis requires thorough preoperative bone health assessment and the application of targeted optimization strategies. DXA-based BMD evaluation is recommended in all patients aged ≥65 years and in younger patients with risk factors for poor bone quality. Surgical techniques should focus on enhancing PS fixation and mitigating implant-related complications by optimizing the screw trajectory, diameter, and length; appropriate sacral fixation; selective cement augmentation; and meticulous preservation of vertebral endplates. Perioperative pharmacological management, comprising anabolic agents followed by antiresorptive treatments, further enhances fusion outcomes and mechanical stability. An integrated approach combining structured bone health assessment, optimized surgical techniques, and appropriate pharmacologic management is essential for improving outcomes in osteoporotic spine surgery.
Key Points
Bone health should be evaluated in all patients before elective spinal reconstructive surgery.
Dual-energy X-ray absorptiometry-based bone mineral density evaluation is recommended in all patients aged =65 years and for younger patients with risk factors prior to spinal instrumentation.
Optimization of pedicle screw trajectory, diameter, and length; appropriate sacral fixation; and selective cement augmentation enhances fixation strength in osteoporotic spines.
Perioperative anabolic therapy, followed by anti-resorptive agents when indicated, lowers implant-related complications.
Notes
Conflict of Interest
CNK and HJS serve as Editorial Board members of the Asian Spine Journal but have no role in the decision to publish this article. Except for that, no other potential conflict of interest relevant to this article was reported
Author Contributions
Conceptualization: HJS, CNK. Data curation: HJS, SCP, WRC. Formal analysis: HJS, SCP, WRC. Methodology: HJS, CNK. Project administration: HJS, CNK. Visualization: HJS, SCP, WRC. Writing–original draft: HJS. Writing–review & editing: HJS, SCP, WRC, CNK. Final approval of the manuscript: all authors.